In a 50-year study of more than 17,000 British people who were followed since birth, researchers from the RAND Labor and Population program found that psychological problems during childhood were related to measurable social and financial deficits later in life.

By age 50, those who had experienced serious psychological problems as children had family incomes that were 25% smaller than those of their peers who didn't have the same issues. Kids who had serious psychological problems — such as depression, anxiety, substance abuse or other mental disorders that caused moderate or severe 'emotional maladjustment' as determined by a doctor — were also less likely to have stable personal relationships or to be married by 50.

"These findings demonstrate that childhood psychological problems can have significant negative impacts over the course of an individual's life, much more so than childhood physical health problems," said James P. Smith, one of the study's authors and a senior economist at RAND, in a statement.

"The findings suggest that increasing efforts to address these problems early in children may have large economic payoffs later in life."

The impact of childhood psychological problems began surfacing early on: by age 23, people with childhood mental health issues had household incomes that were already 19% lower than those of their peers who didn't have such childhood problems.

Some of that disparity may have to do with the fact that affected kids were 6% less likely to be in a stable relationship as adults, and so they missed out on having dual-income families. Another factor: those who had childhood psychological problems were also 11% less likely to work, and held fewer jobs continuously — a significant detail, considering that people tend to increase their income by changing jobs to seek better opportunities.

Researchers also found that people with psychological problems in youth scored lower on personality measures of "agreeableness" and "conscientiousness" by age 50 and showed reduced cognitive abilities — all factors that may have contributed to their social and economic shortfalls.

By contrast, when the participants' childhood physical health problems were considered, researchers found that major health problems were associated with 9% lower household income, while minor health problems attributed to a 3% reduction, compared with people who didn't have health issues in childhood. Why the difference? Unlike physical problems, mental health issues may occur earlier in childhood and persist, researchers say.

The current study used data from the long-term National Child Development Study, which periodically gathered information from its 17,000 participants, all born in the first week of March 1958, including measures of physical and psychological health in childhood and tests of cognitive ability and personality in adulthood. The researchers say that over a lifetime, early psychological health may be much more important than physical health.

A separate, earlier study involving a U.S. population, and co-authored by Smith, found that psychological problems in childhood cost Americans $2.1 trillion over their lifetimes in lost income.